Digital data recording apparatus

ABSTRACT

There is provided a digital data recording apparatus, which can transmit a recording data via a rotary transformer without receiving an influence of a recording data rate and low frequency cut-off, and can perform high-quality digital recording with a simple configuration.  
     The digital data recording apparatus includes: modulation means for modulating a recording clock by a recording data; reference level setting means for setting a reference voltage and a reference current in signal processing based on a reference clock having a multiple cycle of the cycle of the recording clock when the reference clock is supplied via the rotary transformer; demodulation means for obtaining a demodulation signal from a modulation signal when the modulation means supplies the modulation signal via the rotary transformer; recording signal generating means for generating a recording signal from the demodulation signal; and recording means for recording the recording signal on a recording medium. The demodulation means includes: signal forming means for obtaining a modulation signal and an inverted modulation signal from the modulation signal; first and second saw-tooth wave generators for obtaining first and second saw-tooth wave signals from the modulation signal and the inverted modulation signal when the reference current is supplied from the reference level setting means; and a mixer for mixing the first and second saw-tooth wave signals, and obtains the demodulation signal based on an output signal from the mixer and the reference voltage from the reference level setting means.

TECHNICAL FIELD

[0001] The present invention relates to a digital data recordingapparatus, and in particular, to a digital data recording apparatus,which records a recording data on a magnetic tape using a rotary head.

BACKGROUND ART

[0002] In the case of handling digital information via a magneticrecording unit, there is a need of recording a binary information havinglogical values “1” and “0” on a magnetic medium without an error, andregenerating the binary information recorded from the magnetic mediumwithout an error. In this case, a pulse string having binaryinformation, that is, logical values “1” and “0” is converted into arecording data by an encoder, and a rectangular wave currentcorresponding to the recording data flows through a recording head. Bydoing so, a recording signal having a pulse string of logical values “1”and “0” is recorded in accordance with the presence or absence ofmagnetization reversal on the magnetic medium. Further, whenregenerating, the presence of regenerative pulse signal at apredetermined time zone is detected based on a synchronizing signal, andthen, the recording signal is regenerated by a decoder based on thedetected pulse string.

[0003] In this case, a recording data is converted by the encoder whenrecording, and the minimum continuation length Tmin of the logical value“1” of the obtained recording data receives a limitation by a pulseinterference generated in recording/regenerating process. For thisreason, the minimum continuation length Tmin is hard to be set to apredetermined value or less. On the other hand, the maximum continuationlength Tmax influences a synchronizing ability successivelyself-corrected by a regenerative detection pulse generated at thelogical value “1” of the recording data, and a so-called low frequencycut-off is generated in signal transmission by a rotary transformer.

[0004] Moreover, in this type of digital data recording apparatus, in ahigh transfer rate, an edge portion of waveform pattern of recordingcurrent weakens by a permeability of the recording head and frequencycharacteristics of a recording amplifier; as a result, a high frequencycomponent is deteriorated. For this reason, a phase of a shortwavelength side is delayed with respect to a long wavelength side of amagnetizing pattern recorded on a magnetic tape, and therefore, aso-called peak shift occurs as well known.

[0005] In order to solve the problem of the low frequency cut-off by therotary transformer of the above conventional digital data recordingapparatus, the following system has been proposed. According to thesystem, the recording data is modulated at a recording clock, and then,is transmitted by a rotary transformer in a state of having no directcurrent component, and further, is demodulated using a delay linecorresponding to a data rate. However, according to this method, in thecase where the data rate is greatly variable, the configuration of thesystem becomes complicated, and it is impossible to perform a highlyaccurate demodulating operation.

[0006] Moreover, in order to suppress the peak shift to the lowestlimitation, the following system has been proposed. According to thesystem, resonance of the recording head and an HPF are used, andthereby, a high frequency component of recording data is enhanced.However, according to this system, it is impossible to suitably adapt tovariations of data rate.

DISCLOSURE OF THE INVENTION

[0007] The present invention has been made in view of the above problemof this type of digital recording apparatuses in the prior art.Therefore, an object of the present invention is to provide a digitaldata recording apparatus, which can transmit a recording data via arotary transformer without receiving an influence of the recording datarate and low frequency cut-off, and can suitably enhance a highfrequency component of the recording data in accordance with therecording data rate, and further, has a simple configuration.

[0008] A digital data recording apparatus of the present inventioncomprises:

[0009] modulation means for modulating a recording clock by a recordingdata;

[0010] reference level setting means for setting a reference voltage anda reference current in signal processing based on a reference clockhaving a multiple cycle of the cycle of the recording clock when thereference clock is supplied via a signal transmission line having lowfrequency cut-off characteristics;

[0011] demodulation means for obtaining a demodulation signal from amodulation signal when the modulation means supplies the modulationsignal via the signal transmission line having low frequency cut-offcharacteristics;

[0012] recording signal generating means for generating a recordingsignal from the demodulation signal; and

[0013] recording means for recording the recording signal on a recordingmedium,

[0014] the demodulation means having: signal forming means for obtaininga modulation signal and an inverted modulation signal from themodulation signal; first and second saw-tooth wave generators forobtaining first and second saw-tooth wave signals from the modulationsignal and the inverted modulation signal when a reference current issupplied from the reference level setting means; and a mixer for mixingthe first and second saw-tooth wave signals, and obtaining thedemodulation signal based on an output signal from the mixer and thereference voltage from the reference level setting means.

[0015] Further, the digital data recording apparatus of the presentinvention is provided with high frequency enhancement waveformgenerating means for generating a high frequency enhancement waveformwith respect to the demodulation signal, and the high frequencyenhancement waveform is superposed on the demodulation signal so as togenerate a recording signal.

[0016] Further, the digital data recording apparatus of the presentinvention is provided with envelope detection means for detecting anenvelope level of the modulation signal, and a recording current forrecording the recording signal on a recording medium is controlled inaccordance with the envelope level obtained from the envelope detectionmeans.

[0017] According to the present invention, by a simple configuration,the modulation signal of the recording data is transmitted via a signaltransmission line having low frequency cutoff characteristics such as arotary transformer without being influenced by the recording data rateand low frequency cut-off, and the modulation signal after beingtransmitted via the signal transmission line having low frequencycut-off characteristics is demodulated. Further, a high frequencycomponent of the demodulation signal is properly enhanced in accordancewith the recording data rate, and peak shift is prevented with respectto a recording magnetizing pattern to thereby perform high-qualitydigital recording.

BRIEF DESCRIPTION OF DRAWINGS

[0018]FIG. 1 is a circuit diagram showing a configuration of a digitaldata recording apparatus according to the embodiment of the presentinvention;

[0019]FIG. 2 is a timing chart showing signal waveforms of respectivesections of FIG. 1;

[0020]FIG. 3 is a timing chart showing a recording data modulatingoperation of FIG. 1;

[0021]FIG. 4 is a timing chart showing a high frequency enhancementwaveform generating operation of FIG. 1;

[0022]FIG. 5 is a diagram explaining reference voltage level setting ofFIG. 1; and

[0023]FIG. 6 is a diagram explaining detection of a recording signalincluding a low band component.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] An embodiment of the present invention will be described belowwith reference to FIG. 1 to FIG. 6.

[0025]FIG. 1 is a circuit diagram showing a configuration of a digitaldata recording apparatus according to the embodiment of the presentinvention, FIG. 2 is a timing chart showing a signal waveform of eachsection of the digital recording apparatus according to the embodiment,FIG. 3 is a timing chart showing a recording data modulating operationof the embodiment, FIG. 4 is a timing chart showing a high frequencyenhancement waveform generating operation of the embodiment, FIG. 5 is adiagram explaining reference voltage level setting of the embodiment,and FIG. 6 is a diagram explaining detection of a recording signalincluding a low band component.

[0026] According to this embodiment, as shown in FIG. 1, the digitaldata recording apparatus is provided with a modulation signal outputcircuit 2 and a reference clock output circuit 1. More specifically, themodulation signal output circuit 2 modulates a recording clock Fc by arecording data Fd so as to output a modulation data Fm1. The referenceclock output circuit 1 generates a reference clock Fco from therecording clock Fc, and outputs it. Further, the reference clock outputcircuit 1 is connected with a reference signal setting circuit 3 forsetting a reference signal based on the reference clock Fco via a rotarytransformer 8 a. The modulation signal output circuit 2 is connectedwith a demodulation signal output circuit 5 for demodulating andoutputting the modulation signal Fm1 via a rotary transformer 8 b. Thedemodulation signal output circuit 5 is connected with the referencesignal setting circuit 3.

[0027] In addition, the demodulation signal output circuit 5 isconnected with a high frequency enhancement waveform generating circuit6 for generating a high frequency enhancement waveform. An outputterminal of the demodulation signal output circuit 5 is connected to oneinput terminal of a mixer 7, and an output terminal of the highfrequency enhancement waveform generating circuit 6 is connected to theother input terminal of the mixer 7. A recording data Fr is outputtedfrom the mixer 7, and then, is inputted to a recording head 10, which isso arranged as to closely face a recording medium 11.

[0028] According to this embodiment, in the modulation signal outputcircuit 2, an exclusive OR circuit 14 performs an operation of anexclusive logical sum of the recording data Fd and the recording clockFc. An output signal of the exclusive OR circuit 14 is set to apredetermined voltage level by a voltage control amplifier 15 connectedto the output terminal of the exclusive OR circuit 14. The voltagecontrol amplifier 15 outputs a modulation data Fm1 as shown in FIG.2(3).

[0029] The continuation length of logical value “1” of the modulationdata Fm1 is a minimum continuation length To of the logical value “1” ofthe recording data Fd, and ½ continuation length of the To, that is, (½)To. Therefore, the continuation length is sufficiently small as comparedwith a continuation length 3 To of the logical value “1” of therecording data Fd. The modulation data Fm1 is transmitted to thedemodulation signal output circuit 5 by the rotary transformer 8 bwithout generating a low frequency cut-off.

[0030] On the other hand, in the reference clock output circuit 1, acycle of the recording clock Fc is doubled by a flip-flop 12, andthereafter, is amplified by an amplifier 13 connected to the flip-flop12. A reference clock Fco as shown in FIG. 2(4) is outputted from theamplifier 13, and then, is inputted to the reference signal settingcircuit 3 via the rotary transformer 8 a.

[0031] In the reference signal setting circuit 3, the reference clockFco is amplified by an amplifier 16, and thereafter, is inputted to asaw-tooth wave generator 17 connected to the amplifier 16. The saw-toothwave generator 17 outputs a saw-tooth wave signal Fs1 for setting areference voltage level, and then, the saw-tooth wave signal FS1 isinputted to an envelope detector 19 connected to the saw-tooth wavegenerator 17.

[0032] The envelope detector 19 is connected with a differentialamplifier 20, and a reference voltage Vo is applied to a non-invertinginput terminal of the differential amplifier 20 from a battery 22.

[0033] Thus, when a voltage value of the peak of the saw-tooth wavesignal Fs1 detected by the envelope detector 19 reaches a referencevoltage Vo, the logical value of output signal of the differentialamplifier 20 becomes “1”, and then, a reference current Io is outputtedfrom a voltage-current converter 18 connected to the differentialamplifier 20. The reference current Io is inputted to the saw-tooth wavegenerator 17, and the reference signal setting circuit 3 isservo-controlled in a state of setting the reference voltage Vo and thereference current Io.

[0034] By the way, the modulation data Fm1 inputted to the demodulationsignal output circuit 5 is inputted to an amplifier 23, and then, theamplifier 23 outputs the modulation data-Fm1 and an inverted modulationdata [−Fm1]. The modulation data Fm1 is inputted to a saw-tooth wavegenerator 24 connected to the amplifier 23; on the other hand, theinverted modulation data [−Fm1] is inputted to a saw-tooth wavegenerator 25 connected to the amplifier 23.

[0035] When the reference current Io is supplied from the referencesignal setting circuit 3 to the saw-tooth wave generator 24, thesaw-tooth wave generator 24 outputs a saw-tooth wave signal Fms1 asshown in FIG. 2(6), and likewise, the saw-tooth wave generator 25outputs a saw-tooth wave signal Fms2 as shown in FIG. 2(7).

[0036] These saw-tooth wave generators 24 and 25 are connected with oneinput terminal and the other input terminal of a mixer 26, respectively,and the saw-tooth wave signals Fms1 and Fms2 are mixed by the mixer 26.The mixed signal is inputted to a non-inverting input terminal of adifferential amplifier 27 connected to the mixer 26. On the other hand,a ¾-voltage value (¾) Vo of the reference voltage Vo is applied to aninverted input terminal of the differential amplifier 27 from anattenuator 21 connected to the non-inverting input terminal of thedifferential amplifier 20 of the reference signal setting circuit 3.

[0037] Thus, when the voltage value of the mixed signal outputted fromthe mixer 26 exceeds (¾) Vo, the differential amplifier 27 outputs adetection pulse Fd1 as shown in FIG. 2(8). The detection pulse Fd1 isinputted to a clock terminal of a flip-flop 28 connected to thedifferential amplifier 27, and the flip-flop 28 outputs a demodulationdata Fdm as shown in FIG. 2(9). Then, the demodulation data Fdm is setto a predetermined signal level by a voltage control amplifier 29connected to the flip-flop 28. In this case, the voltage controlamplifier 29 controls an amplification degree in accordance with anenvelope level of the modulation data Fm1 detected by an envelopedetector 30.

[0038] On the other hand, in the high frequency enhancement waveformgenerating circuit 6, the exclusive OR circuit 31 carries out anoperation of the exclusive logical sum of the modulation data Fm1 fromthe amplifier 23 of the demodulation signal output circuit 5 and thedemodulation data Fdm from the flip-flop 28. By doing so, a modulationsignal Fm3 as shown in FIG. 2(11) is obtained. Further, the exclusive ORcircuit 33 carries out an operation of the exclusive logical sum of asignal such that the demodulation data Fdm from the flip-flop 28 isdelayed by a delay circuit 32 and the demodulation data Fdm, andthereby, an edge pulse Fe as shown in FIG. 2(10) is obtained.

[0039] Moreover, in the high frequency enhancement waveform generatingcircuit 6, a latter stage of the exclusive OR circuit 31 is providedwith a latch circuit having flip-flops 34 to 37 connected in series. Anoutput terminal of the exclusive OR circuit 31 is connected to eachclock terminal of the flip-flops 34 to 37; on the other hand, an outputterminal of the exclusive OR circuit 33 is connected to each resetterminal of the flip-flops 34 to 37.

[0040] The latch circuit carries out a latch operation according to themodulation signal Fm3 while resetting by the edge pulse Fe, and theflip-flops 34 to 37 output latch data F11 to F14 as shown in FIG. 2(12)to FIG. 2(15), respectively.

[0041] Further, the high frequency enhancement waveform generatingcircuit 6 is provided with exclusive OR circuits 38 and 39, whichindividually have one input terminal connected to the output terminal ofthe flip-flop 28 of the demodulation signal setting circuit 5 and theother input terminal connected to each output terminal of the flip-flops35 and 37.

[0042] The exclusive OR circuit 38 carries out an operation of theexclusive logical sum of the demodulation data Fdm shown in FIG. 2(9)and the latch data F12 shown in FIG. 2(13) to thereby obtain amodulation data Fm4 as shown in FIG. 4(16). The modulation data Fm4 isinputted to one input terminal of a voltage control amplifier 40connected to the exclusive OR circuit 38.

[0043] Moreover, the exclusive OR circuit 39 carries out an operation ofthe exclusive logical sum of the demodulation data Fdm shown in FIG.2(9) and the latch data F14 shown in FIG. 2(15) to thereby obtain amodulation data Fm5 as shown in FIG. 4(17). The modulation data Fm5 isinputted to the other input terminal of the voltage control amplifier 40connected to the exclusive OR circuit 39.

[0044] According to this embodiment, in the voltage control amplifier40, a summing operation is carried out with respect the inputtedmodulation data Fm4 and modulation data Fm5, and then, a high frequencyenhancement waveform Fb having a width corresponding to a data rate isgenerated. On the other hand, the signal level of the demodulation dataFdm outputted from the flip-flop 28 is adjusted and controlled by thevoltage control amplifier 29. The demodulation data Fdm having thecontrolled signal level is inputted to one input terminal of the mixer7, and the high frequency enhancement waveform Fb from the voltagecontrol amplifier 40 is inputted to the other input terminal of themixer 7.

[0045] Thus, a recording data Fr as shown in FIG. 4(18) is generated bythe demodulation data Fdm having a signal level controlled by the mixer7 and the high frequency enhancement waveform Fb. A suitable highfrequency enhancement waveform Fb corresponding to the recordingcondition is added to the recording data Fr. Therefore, the high-qualityrecording data Fr outputted from the mixer 7 is recorded on therecording medium 11 by the recording head 10.

[0046] In this case, with respect to the recording data Fr, a referencecurrent level Io of the recording data Fr shown in FIG. 4 and a currentlevel Ib of the high frequency enhancement waveform Fb are set to theoptimum value corresponding to the recording condition by the voltagecontrol amplifiers 29 and 40, respectively. Therefore, it is possible toperform high-quality digital recording in which high frequencyenhancement is suitably made in accordance with recording conditions.

[0047] In general, in the case of detecting an amplitude of recordingdata, as shown in FIG. 6, in order to stably record a recording dataincluding a range from a high frequency component to a low frequencycomponent close to direct current component, a time constant ofdetection must be made large. However, if the time constant of detectionis made large, it is difficult to follow recording start and recordingcompletion.

[0048] According to this embodiment, as shown in FIG. 2(3), thecontinuation length of the signal logical value “1” of the modulationdata Fm1 is only the minimum continuation length To and ½ continuationlength (½) To of the signal logical value “1” of the recording data Fd.Further, the time constant of detection is set to a smaller valueconvenient for the follow-up to the continuation length To, so that itis possible to most suitably follow recording start and recordingcompletion.

[0049] As described above, according to this embodiment, the modulationsignal output circuit 2 modulates the recording clock Fc by therecording data Fd, and the reference signal setting circuit 3 sets areference signal level based on the reference clock Fco having a cycletwice as much as the cycle of the recording clock Fc. Further, thedemodulation signal output circuit 5 demodulates the modulation signalFm1 based on the saw-tooth wave signal Fms1 corresponding to themodulation signal Fm1 obtained by the modulation signal output circuit 2and the inverted saw-tooth wave signal Fms2 corresponding to an invertedsignal of the modulation signal to thereby obtain a demodulation dataFdm. The high frequency enhancement waveform generating circuit 6generates a high frequency enhancement waveform Fb corresponding to thedemodulation data Fdm, and the mixer 7 superposes the high frequencyenhancement waveform Fb on the demodulation data Fdm, so that arecording signal Fr is obtained.

[0050] Therefore, according to this embodiment, with a simpleconfiguration using no special circuit element, it is possible totransmit the modulation data Fm1 of the recording data Fd via the rotarytransformer 8 b without receiving an influence of recording data rateand low frequency cut-off, and to demodulate the data aftertransmission. Further, a high frequency component of the demodulationdata Fdm is securely enhanced in accordance with the recording datarate, and peak shift is prevented with respect to a recordingmagnetizing pattern, so that it is possible to perform high-qualitydigital recording.

[0051] The above embodiment has described the case of forming two highfrequency enhancement waveforms, that is, the high frequency enhancementwaveform Fb1 and the high frequency enhancement waveform Fb2 as shown inFIG. 4(18). The present invention is not limited to the aboveembodiment, and the number of high frequency enhancement waveforms maybe increased and decreased. Moreover, the current level does not have tobe controlled in common as the above embodiment, and may be controlledindependently.

[0052] Further, the above embodiment has described the case where aclock having a cycle twice as much as the cycle of the recording clockis used as the reference clock when demodulating the recording datawhose recording clock is modulated, and the detection level of thesaw-tooth wave is set to (¾) Vo. The cycle and detection level havingother multiplied values may be used In this case, if the reference clockis set to n=1, the detection level is 0.75 n. Thus, in the case wherethe recording clock is used, the reference clock becomes n=2; so that avoltage of 1.5 times as much as the reference voltage Vo may be used asthe detection level. Further, as to the coefficient 0.75, an arbitraryvalue from 0.5 to 1.0 may be used when accurate judgment is possible.

[0053] According to the present invention, the modulation meansmodulates the recording clock by the recording data, and the referencesignal setting means sets a reference signal level in signal processingbased on the reference clock having a multiple cycle of the cycle of therecording clock. Further, the demodulation means demodulates themodulation signal based on the saw-tooth wave signal corresponding tothe modulation signal obtained by the modulation means and the invertedsaw-tooth wave signal corresponding to an inverted signal of themodulation signal to thereby obtain a demodulation signal. The highfrequency enhancement waveform generating means generates a highfrequency enhancement waveform corresponding to the demodulation signal,and the recording signal generating means superposes the high frequencyenhancement waveform on the demodulation signal to generate therecording signal. Therefore, in spite of a simple configuration, it ispossible to transmit the modulation signal of the recording data via therotary transformer without receiving an influence of the recording datarate and low frequency cut-off. Further, a high frequency component ofthe demodulation signal generated by demodulating the modulation signalafter transmission via the rotary transformer is securely enhanced inaccordance with the recording data rate, and peak shift is preventedwith respect to a recording magnetizing pattern, so that it is possibleto perform high-quality digital recording.

1. A digital data recording apparatus, characterized by including:modulation means for modulating a recording clock by a recording data;reference level setting means for setting a reference voltage and areference current in signal processing based on a reference clock havinga multiple cycle of the cycle of the recording clock when the referenceclock is supplied via a signal transmission line having low frequencycut-off characteristics; demodulation means for obtaining a demodulationsignal from a modulation signal when the modulation means supplies themodulation signal via the signal transmission line having low frequencycut-off characteristics; recording signal generating means forgenerating a recording signal from the demodulation signal; andrecording means for recording the recording signal on a recordingmedium, the demodulation means having: signal forming means forobtaining a modulation signal and an inverted modulation signal from themodulation signal; first and second saw-tooth wave generators forobtaining first and second saw-tooth wave signals from the modulationsignal and the inverted modulation signal when the reference current issupplied from the reference level setting means; and a mixer for mixingthe first and second saw-tooth wave signals, and obtaining thedemodulation signal based on an output signal from the mixer and thereference current from the reference level setting means.
 2. The digitaldata recording apparatus according to claim 1, characterized by furtherincluding a high frequency enhancement waveform generating means forgenerating a high frequency enhancement waveform with respect to thedemodulation signal, the high frequency enhancement waveform beingsuperposed on the demodulation signal so as to generate a recordingsignal.
 3. The digital data recording apparatus according to claim 1 or2, characterized by further including envelope detection means fordetecting an envelope level of the modulation signal, a recordingcurrent for recording the recording signal on a recording medium beingcontrolled in accordance with an envelope level obtained from theenvelope detection means.